Okay Ive built the din exactly as you posted it here. (Except I have been using KO'd Wiz / Tgods / 10fcr 15 Dex ring)
Merc exactly as you listed it. (Ive used both Tal mask and Dream) he dies in chaos either way..
I tried using the act 3 merc instead, but lower life and just didnt seem as helpful as the act 5 merc.
1) My #1 MAIN problems is that my merc dies

He has broad sword lawbringer, CoH, and Tal mask / Dream helm. (Both helms die). He is lvl 85
2)
Its been 5 levels or so since I tried fighting the Fire Lords in chaos
without my wiz...... But when I was wearing Hoz, and they have
Conviction.... They lower my Res to below max... So I actually take
damage from them!!!!!
So far using wiz, I have not taken any
dmg from anything in hell hardly... I do about 2k less damage though.
(Not that it matters, I still kill everything easy in a 4 player game
of friends).
3) Do you actually use the Oak Sage from Hoto?
Its cheap to repair.. I was just curious if anyone ever used it? Cant
BO it, so it dies easy / fast.
items on either the merc nor the player are negotiable. To get the
results listed you must follow the guide exactly. I've made this
character ESCL exactly to these specs and it runs great.